Effect of fluorescein instillation on the pre-corneal tear film stability.

Non-invasive tear film break-up time (NIBUT) was measured in nine normal subjects to investigate the effect of fluorescein instillation of tear film stability. It was found that fluorescein instillation reduced the tear film stability in the treated group, compared with the control group (P less than 0.05). It is, therefore likely that the tear film stability may be greater than had hitherto been suggested by the fluorescein method.